1. Field of the Invention
The invention relates to longitudinally water-tight cables and somewhat more particularly to communication cables having in their interior a filling material containing a water-repellant substance and relatively small gas bubbles embedded therein.
2. Prior Art
Longitudinally water-tight cables having in their interior a filling material containing a water-repellant substance and relatively small gas bubbles embedded therein are known from German Offenlegungsschrift No. 27 16 524. However, the emplacement of the gas bubbles in such filling material within these cables is such that their position in the filling material is not stable without further ado and there is a danger that larger gas bubbles (which have an unfavorable influence on electrical properties of a cable) may form at specific locations because of the migration and subsequent coupling of the smaller gas bubbles into a larger gas bubble. To avoid this drawback, the prior art attempted to stabilize the respective gas bubble positions by providing supportive components, in the form of fibers, within the filling material. However, the preparation of such added fibers and their subsequent incorporation into water-repelling filling substances requires an additional outlay. Further, the desired effect of such fibers is only assured when the fiber size is approximately of the same magnitude as the size of the small gas bubbles. Fibers which are too large disrupt electrical properties of a cable in an undesirable manner so that a very fine division of the additional fiber components becomes necessary.